Many reasons exist for dispensing liquid, such as hot melt adhesives, in the form of a thin filament or fiber with a controlled pattern. Conventional patterns used in the past have been patterns involving a spiraling of the filament by impacting the filament with jets of process air. The nozzles used to achieve this spiraling effect can be obtained from Nordson Corp., Westlake, Ohio under the trademarks Controlled Fiberization™, CF™, or Summit™. Controlled fiberization techniques are especially useful for accurately covering a wider region of a substrate with adhesive dispensed as single filaments or as multiple side-by-side filaments from nozzle passages having small diameters, such as on the order of 0.010 inch to 0.060 inch. This is especially useful on very narrow substrates, such as on elastic strands, e.g., Lycra®, used in the manufacture of disposable diapers or other disposable products. Other adhesive filament dispensing techniques and apparatus have been used for producing a non-overlapping, oscillating pattern of adhesive on a substrate or, in other words, a stitching pattern in which the adhesive moves back-and-forth generally in a zig-zag form on the substrate.
Various types of nozzles or die tips, such as those of the type described above, have been used to dispense adhesive onto one or more elastic strands. For such applications, the strand or strands typically need to be guided at specific spaced apart positions as the adhesive is discharged onto the strand or strands. Even a single strand needs to be guided and stabilized to ensure accurate placement of the adhesive on the strand. For this purpose, strand guides may take the form of rollers that are fixed to the dispensing module or some other fixed structure, or alternatively they may take the form of a notched structure integrated with or otherwise mounted proximate the nozzle. An exemplary dispensing module having an integrated strand guide is disclosed in U.S. Pat. No. 7,578,882, assigned to the assignee of the present invention, and the disclosure of which is hereby expressly incorporated by reference herein in its entirety. In this form of strand guide, one or more notches respectively guide one or more elastic strands as the strand or strands move in the machine direction or, in other words, lengthwise along a manufacturing line. While integrated notched structures work acceptably for two or more strands running in parallel, a minimum spacing is required between the strands. The minimum spacing is designed to ensure that the flow of adhesive and process air intended for one strand does not interfere with the adhesive and process air intended for an adjacent strand. The spacing requirement imposes constraints on the design of products, such as diapers, that may require elastic strands to be spaced from one another by distances smaller than those allowed by current nozzles.
It would therefore be desirable to provide a method of dispensing adhesive onto individual strands within a group of strands in a manner that achieves the ability to even more closely space the strands on an adhered substrate than the existing technology.